In our business, we use Google Apps for all of our email, as we do not host our own mail server. As a result, most of our employees have their GoogleApps emails forward to their regular Gmail accounts, and also interact with their GApps emails through their regular Gmail accounts ("send as", etc.) as it is easier than juggling two accounts, or two signed-in browsers, etc.

One of our company directors has an issue where some of his recipients will receive his email with the "via" included, i.e. bob@company.com via bob.smith@gmail.com. This only applies to SOME recipients, and which recipients parse emails this way seems to be completely random -- it's only certain mail servers that dig up the via information. The rest of the servers only see the bob@company.com email address, and that's the only address that shows up in the sender info.